Radio communication system

INCORPORATION BY REFERENCE

0001The present application claims priority from Japanese application JP2004-240816 filed on Aug. 20, 2004, the content of which is hereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION

0002The present invention relates to a radio communication system which includes a line controller, base stations, and mobile stations, and more particularly, to a radio communication system which has an improved architecture for assignment of a communication channel to a mobile station.

0003A standard has been established for a multi-channel access (MCA) radio system for airports which play an important role of ensuring the security of aircrafts existing in airports and the comfort of users. For example, see a document entitled “AIRPORT DIGITAL MOBILE TELECOMMUNICATION SYSTEM,” ARIB STD T-87, October 2003 by Association of Radio Industries and Business (ARIB).

0004In a system conforming to the foregoing standard, an airport, which constitutes a basic unit, is composed of control station facilities, base station facilities, and mobile station facilities, wherein communications are made between a domestic terminal and a mobile station or between mobile stations (through a base station or directly) using a 400 MHz band. The system employs a quadruple TDM/TDMA scheme which separates a single radio carrier on a frame-by-frame basis and groups the frames into four slots for providing multiple channels. The system also employs a n/4 shifted QPSK modulation scheme. Specifically, a base station is assigned a single or a plurality of radio carriers (pair waves) from a 400 MHz band which is an available frequency band. Each of a downlink radio carrier f<b>1</b> and an uplink radio carrier f<b>2</b> is divided into frames which are sub-divided into slots which are then allocated to a control channel and a communication channel.

0005For special requirements of operational communications within an airport such as consistent security for aircraft, this system is also required to permit ensured emergency communications and preferential connections for crucial or important communications.

0006For example, in a communication system which employs a multi-channel access (MCA) scheme as described above, a plurality of communication channels are commonly used by a multiplicity of users.

0007In such a multi-channel access based communication system, a base station, in response to a connection request from a mobile station, designates a communication channel assigned from a line controller for the mobile station, thereby permitting the mobile station to make communications through the designated communication channel.

0008In this event, upon receipt of the connection request from the mobile station, the base station requests the line controller to assign a communication channel, thereby acquiring information on the communication channel to be designated for the mobile station, from the line controller.

0009JP-A-11-262044 discloses a communication channel assignment method which enables a quick response to an assignment request for one or a plurality of channels from a mobile station in a multi-carrier TDMA base station which selectively combines a plurality of carrier frequencies with a plurality of time slots formed in time division at each carrier frequency to establish a plurality of radio communication channels. This prior art system does not have a line controller, but the base station contains a management table which is registered with one or a plurality of idle channels selected from a plurality of communication channels as candidate channels. Upon receipt of a channel assignment request from a mobile station, the base station references the management table to select a communication channel which satisfies particular communication quality conditions from the candidate channels for assignment to the requesting mobile station. The level of a received radiowave on each channel is relied on to determine whether or not the channel is idle. Then, a candidate channel, determined to be an idle channel based on the level of a radiowave received thereon, is used to communicate with at least one mobile station, thereby checking whether or not this is an effective candidate channel.

SUMMARY OF THE INVENTION

0010However, in the conventional airport digital mobile communication system as described above, since processing for assigning a communication channel is not carried out until a connection is requested from a mobile station, the system inconveniently consumes a long time for designating a communication channel for the mobile station. In the radio communication system disclosed in JP-A-11-262044, while a channel request can be quickly responded with the aid of the management table which is used by the base station to register idle channel candidates, the radio communication system of JP-A-11-262044 does not have a line controller, so that it is necessary to determine whether or not each channel is idle by checking the level of a received radiowave on that channel. In other words, the base station must search idle channel candidates by itself at all times to create and constantly update the management table. Further, for candidate channels which have been determined to be idle based on the level of radiowaves received thereon, the base station must check whether or not each candidate channel is effective by communicating with at least one mobile station on the candidate channel, from which it seems impossible to avoid complicated control and increased circuit scale. In addition, this radio communication system is not sufficient from a viewpoint of usability because it does not consider a preferential connection request which is required for special applications such as an airport application.

0011It is therefore an object of the present invention to provide a highly usable radio communication system and radio communication method which are capable of quickly designating a communication channel for a mobile station in response to a connection request from the mobile station through a simple control with the aid of a line controller.

0012It is another object of the present invention to provide a radio communication system and a radio communication method which are capable of responding to special requirements in a special environment such as an airport.

0013A radio communication system according to one aspect of the present invention includes at least one base station, a plurality of mobile stations accommodated in the base station, and a line controller connected to the base station for managing or keeping tracking of communication channels possessed by the radio communication system. The line controller includes a first memory for managing or keeping track of each of the communication channels of the system for each base station as to whether the communication channel is occupied or idle. The base station includes a second memory for storing at least one of idle communication channels stored in the first memory as a reserved channel(s). The base station is responsive to a connection request generated from an arbitrary calling mobile station of the mobile stations and including designation of at least one called mobile station to designate the reserved channel stored in the second memory of the base station as a communication channel for at least the calling mobile station to establish a connection with the calling mobile station.

0014Here, the number of line controllers, the number of base stations, and the number of mobile stations may be respectively arbitrarily selected. A wired or a wireless communication is made between the base station and the line controller. Also, each of the base stations accommodates or location-registers mobile stations by managing identification information of the mobile stations which are present in the coverage area of the base station. A communication channel is identified, for example, by one or more of the frequency, a spread code when spread coding is applied, a time zone such as a time slot, and the like.

0015A variety of formats may be used for the connection request signal generated from the mobile station.

0016Preferably, the base station designates the reserved channel as a communication channel for the called mobile station as well to establish a connection with the called mobile station.

0017Preferably, the base station includes a connection notification unit for issuing a connection notification related to unconnected and connected mobile stations to the line controller, and the line controller comprises a channel notification unit, responsive to receipt of the connection notification, which shows that unconnected mobile stations include a mobile station which is accommodated in a base station different from the base station, to notify the different base station of a communication channel which should be assigned to the different base station.

0018Preferably, the base station includes a channel notification request unit for requesting the line controller for notification of an idle communication channel which is to be stored in the second memory as the reserved channel, and the line controller includes a channel notification unit responsive to the request for the notification of an idle communication channel from the base station to notify an idle communication channel stored in the first memory to the base station.

0019Here, the base station may request the line controller for notification of a communication channel to be designated in the future at any of various timings. For example, the request may be made at a timing at which the base station is activated, at a timing at which the base station designates a previously notified communication channel for a mobile station.

0020Preferably, the channel notification request unit issues the request for the notification of an idle communication channel when the base station is activated.

0021Preferably, the channel notification request unit issues the request for the notification of an idle communication channel when the reserved channels stored in the second memory have been assigned to communications of mobile stations so that idle channels are not available.

0022A radio communication system according to another aspect of the present invention includes at least one base station, a plurality of mobile stations accommodated in the base station, and a line controller connected to the base station for managing or keeping track of communication channels possessed by the radio communication system. The line controller includes a first memory for managing or keeping track of each of the communication channels of the system for each base station as to whether the communication channel is occupied or idle. The base station includes a second memory for storing at least one of idle communication channels stored in the first memory as a reserved channel(s). Each of the mobile stations includes a connection request unit for issuing a connection request to the base station, including designation of at least one called mobile station and designation of a preference for or a priority of a connection. The system further includes a preferential connection control unit responsive to a connection request having a high connection priority from an arbitrary calling mobile station to secure an idle communication channel from the communication channels possessed by the system to preferentially assign the secured communication channel to a communication associated with the connection request.

0023Here, a variety of information may be used for specifying the priority, for example, information indicating that a connection request should be preferentially handled, information indicating whether or not a connection request should be preferentially handled, or the like.

0024Preferably, the preferential connection control unit is responsive to a connection request having a high connection priority issued from the calling mobile station to preferentially assign a reserved channel stored in the second memory of the base station to the communication associated with the connection request.

0025Preferably, the reserved channels stored in the second memory of the base station include an idle communication channel for a connection request having a high connection priority, and the preferential connection control unit is responsive to a connection request issued from a calling mobile station and having a high connection priority to preferentially assign the idle communication channel for the connection request having a high connection priority stored in the second memory of the base station to a communication associated with the connection request.

0026Preferably, the preferential connection control unit is responsive to a connection request having a high connection priority issued from a calling mobile station to abort a communication through a communication channel being used and preferentially assign the communication channel freed thereby to a communication associated with the connection request when an idle communication channel is not currently available.

0027Thus, when a connection request issued from a mobile station should be preferentially handled but there is no idle communication channel available, a communication channel in use is forcedly freed and preferentially assigned to the mobile station which has requested the connection and another mobile station which is a connection requested party, thereby making it possible to quickly support, for example, an urgently required communication or call.

0028Here, a variety of manners or rules may be used for selecting an occupied communication channel to abort or disconnect an ongoing communication on the channel when no idle communication channel is available. For example, the preferential connection control unit may abort a communication through a communication channel not preferential.

0029A radio communication method according to another aspect of the present invention is used in a radio communication system which includes at least one base station, a plurality of mobile stations accommodated in the base station, and a line controller connected to the base station for managing or keeping track of communication channels possessed by the radio communication system, wherein the line controller includes a first memory for managing or keeping track of each of the communication channels of the system for each base station as to whether the communication channel is occupied or idle, and the base station including a second memory for storing at least one of idle communication channels stored in the first memory as a reserved channel(s). The radio communication method includes the steps of the base station requesting the line controller for notification of an idle communication channel which is to be stored in the second memory as the reserved channel, the line controller notifying the base station of an idle communication channel stored in the first memory in response to the request for the notification of an idle communication channel from the base station, an arbitrary calling mobile station of the mobile stations issuing a connection request including designation of at least one called mobile station to the base station, and the base station, in response to the connection request, designating the reserved channel stored in the second memory of the base station as a communication channel for at least the calling mobile station to establish a connection with the calling mobile station.

0030A radio communication method according to a further aspect of the present invention is used in a radio communication system which includes at least one base station, a plurality of mobile stations accommodated in the base station, and a line controller connected to the base station for managing or keeping track of communication channels possessed by the radio communication system, wherein the line controller includes a first memory for managing each of the communication channels of the system for each base station as to whether the communication channel is occupied or idle, and the base station includes a second memory for storing at least one of idle communication channels stored in the first memory as a reserved channel(s). The radio communication method includes the steps of an arbitrary calling mobile station of the mobile stations issuing to the base station a connection request including designation of at least one called mobile station and designation of a preference for a connection, and the system responding to a connection request having a high connection priority from an arbitrary calling mobile station to secure an idle communication channel from the communication channels possessed by the system to preferentially assign the secured communication channel to a communication associated with the connection request.

0031Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

0032<figref idref="DRAWINGS">FIG. 1</figref> is a block diagram illustrating an exemplary configuration of a radio communication system according to one embodiment of the present invention;

0033<figref idref="DRAWINGS">FIG. 2A</figref> is a diagram showing an example of a memory table for use by a base station;

0034<figref idref="DRAWINGS">FIG. 2B</figref> is a diagram showing an example of a memory table for use by a line controller;

0035<figref idref="DRAWINGS">FIG. 3</figref> is a flow diagram for describing an exemplary processing flow performed in the radio communication system in accordance with one embodiment;

0036<figref idref="DRAWINGS">FIG. 4</figref> is a diagram showing an example of a connection request signal; and

0037<figref idref="DRAWINGS">FIG. 5</figref> is a flow chart illustrating an exemplary processing flow performed in the radio communication system according to one embodiment.

DESCRIPTION OF THE EMBODIMENTS

0038In the following, some embodiments according to the present invention will be described with reference to the accompanying drawings, where like members are designated like reference numerals.

0039<figref idref="DRAWINGS">FIG. 1</figref> illustrates an exemplary configuration of a radio communication system which employs a multi-channel access scheme according to one embodiment of the present invention.

0040The illustrated radio communication system comprises a line controller A<b>1</b>, a plurality of base stations B<b>1</b>, B<b>2</b>, and a plurality of mobile stations C<b>1</b>-C<b>3</b>.

0041The base stations B<b>1</b>, B<b>2</b> comprises a receiver <b>1</b>, <b>11</b> and an associated antenna <b>2</b>, <b>12</b>; a transmitter <b>3</b>, <b>13</b> and an associated antenna <b>4</b>, <b>14</b>; and a control unit <b>5</b>, <b>15</b>, respectively.

0042The line controller A<b>1</b> and each of the plurality of base stations B<b>1</b>, B<b>2</b> are connected to each other, so that the plurality of base stations B<b>1</b>, B<b>2</b> are accommodated in the line controller A<b>1</b>. The mobile stations C<b>1</b>, C<b>2</b> are roaming in a coverage area of the base station B<b>1</b>, so that the mobile stations C<b>1</b>, C<b>2</b> are accommodated in the base station B<b>1</b>. The mobile station C<b>3</b> in turn is roaming in a coverage area of the base station B<b>2</b>, so that the mobile station C<b>3</b> is accommodated in the base station B<b>2</b>.

0043The line controller A<b>1</b> provides a function of managing or keeping track of a line use status of the multi-channel accessing (communication channel use status); a function of creating control information for transmission to the base stations B<b>1</b>, B<b>2</b>; a function of receiving and analyzing control information transmitted from the base stations B<b>1</b>, B<b>2</b>; a function of instructing a mobile station to use a line (use a communication channel) through control information transmitted or received between the mobile station and the line controller A<b>1</b>; and the like.

0044In this embodiment, the line controller A<b>1</b> is connected to the respective base stations B<b>1</b>, B<b>2</b> through wired lines and communicates signals such as the control information to and from the base stations B<b>1</b>, B<b>2</b> through the wired lines.

0045Each of the base stations B<b>1</b>, B<b>2</b> provides a function of communicating signals such as control information, call information and the like over the air with the mobile stations C<b>1</b>-C<b>3</b> accommodated therein; a function of communicating signals such as control information and the like with the line controller A<b>1</b>; and the like.

0046Specifically, each of the base stations B<b>1</b>, B<b>2</b> provides a function of receiving and demodulating control information transmitted over the air from the mobile stations C<b>1</b>-C<b>3</b> through the antenna <b>2</b>, <b>12</b> and receiver <b>1</b>, <b>11</b> to deliver the demodulated control information to the control unit <b>5</b>, <b>15</b>; a function of modulating control information delivered from the control unit <b>5</b>, <b>15</b> by the transmitter <b>3</b>, <b>13</b> to transmit the modulated control information over the air from the antenna <b>4</b>, <b>14</b> to the mobile stations C<b>1</b>-C<b>3</b>; a function of communicating control information and the like with the line controller A<b>1</b> through the control unit <b>5</b>, <b>15</b>; and the like.

0047Each of the mobile stations C<b>1</b>-C<b>3</b> provides a function of communicating signals such as control information, call information and the like over the air with the base station B<b>1</b> or B<b>2</b> which accommodates the mobile station C<b>1</b>-C<b>3</b>; a function of placing a call, receiving a call, displaying a variety of images, and the like in response to an operation made on a key, a button or the like by a user (human).

0048In the radio communication system according to this embodiment, radio communications are made while a plurality of communication channels, which differ, for example, in frequency, time zone (slot number) or the like, are dynamically assigned to the mobile stations C<b>1</b>-C<b>3</b>. In this embodiment, the line controller A<b>1</b> is responsible for the overall assignment and management or keeping track of the communication channels, while each of the base stations B<b>1</b>, B<b>2</b> designates a communication channel for the mobile station C<b>1</b>, C<b>2</b> or C<b>3</b> accommodated therein, and the mobile stations C<b>1</b>, C<b>2</b>, C<b>3</b> make radio communications through respective communication channels assigned thereto.

0049The mobile station can communicate with all other mobile stations in a group to which the mobile station itself belongs in addition to a communication with one mobile station designated thereby as the destination. This communication mode will be described below in connection with an airport digital mobile communication system to which the radio communication system according to this embodiment is applied. For example, all airport workers such as pilots of aircraft, other flight attendants, ground crew, clerks, and the like carry mobile stations, and all vehicles such as cars used for operations in the airport are equipped with mobile stations. The airport digital mobile communication system classifies these airport workers into arbitrary groups such as a group of the pilots of aircraft, a group of other flight attendants, a group of ground crew, and a group of clerks, and a group ID is set to a mobile station carried by each worker. This grouping permits a simultaneous delivery to all mobile stations belonging to an arbitrary group designated by a mobile station or a base station, and a simultaneous delivery from an ordinary mobile station to all mobile stations belonging to a predetermined group(s).

0050The communication channel used herein may be, for example, a call channel for use in telephone calls, data communications and the like.

0051The radio communication system which employs the multi-channel access scheme according to a first embodiment of the present invention will be described with reference to <figref idref="DRAWINGS">FIGS. 1</figref>, <b>2</b>A, <b>2</b>B, <b>3</b>.

0052Referring first to <figref idref="DRAWINGS">FIG. 1</figref>, the line controller A<b>1</b> previously notifies the respective base stations B<b>1</b>, B<b>2</b> of control information which includes information on the assignment of communication channels to be designated for mobile stations from which a connection request is forthcoming thereafter, namely, communication channel assignment information.

0053Each of the base stations B<b>1</b>, B<b>2</b> has a table (memory table) <b>20</b>, for example, in a memory of the control unit <b>5</b>, <b>15</b> for storing the communication channel assignment information notified from the line controller A<b>1</b>.

0054<figref idref="DRAWINGS">FIG. 2A</figref> shows an example of such a memory table <b>20</b> which stores reserved channel information as the communication channel assignment information. The reserved channel information includes two reserved channel numbers, and a flag indicative of whether each reserved channel is occupied or idle. In the shown example, communication channels labeled channel numbers <b>1</b>, <b>5</b>, respectively, are currently assigned to an associated base station as reserved channels, where the flag associated with the communication channel labeled channel number <b>1</b> is “0” indicating that the communication channel is idle, while the flag associated with the communication channel labeled channel number <b>5</b> is 1” indicating that the communication channel is occupied in the associated base station. It should be understood that the reserved channel information can include one or three or more communication channels as required.

0055<figref idref="DRAWINGS">FIG. 2B</figref> shows an example of a memory table <b>22</b> for describing how communication channels are managed in the line controller A<b>1</b>. This memory table <b>22</b> includes a communication channel number for identifying each communication channel, an busy/idle flag, and a preference flag to be described later, for each communication channel in order to manage or keeping track of the communication channels for each base station. The memory table <b>22</b> may include a variety of items to be managed other than the foregoing as required. The line controller A<b>1</b> manages and keeps track of communication channels assigned to each base station at all times as to whether each communication channel is occupied or idle using the memory table <b>22</b>. For example, as will be later described with reference to <figref idref="DRAWINGS">FIG. 3</figref>, when the base station B<b>1</b> assigns a communication channel <b>5</b>, which has been previously assigned to be a reserved channel, to a mobile station which makes a connection request, and sends a connection notification T<b>13</b> indicative of this assignment to the line controller A<b>1</b>, the line controller A<b>1</b> sets the busy/idle flag of the communication channel <b>5</b> within the memory table <b>22</b> to “1,” indicating that the communication channel <b>5</b> is occupied. When the communication channel <b>5</b> is assigned in response to a preferential connection request from a calling mobile station to be described later in connection with a second embodiment, the line controller A<b>1</b> sets the associated preference flag to “1.” The line controller A<b>1</b> keeps track of idle communication channels at all times using the memory table <b>22</b>, such that the line controller A<b>1</b> picks up one idle communication channel from the memory table <b>22</b> for assignment to the base station as a reserved channel as soon as idle communication channels are used up from reserved channels previously assigned to the base stations B<b>1</b>, B<b>2</b>, and sets the busy/idle flag associated with the assigned communication channel to “1” in the memory table <b>22</b>. Likewise, upon receipt of a normal channel connection request (T<b>21</b> in <figref idref="DRAWINGS">FIG. 3</figref>), which is not urgent, from a base station, the line controller A<b>1</b> also picks up an idle communication channel from the memory table <b>22</b>, and notifies the base station of the assigned communication channel (T<b>22</b> in <figref idref="DRAWINGS">FIG. 3</figref>).

0056Communication channels to be previously notified to the respective base stations B<b>1</b>, B<b>2</b> from the line controller A<b>1</b> may be different channels for each of the base stations B<b>1</b>, B<b>2</b>, or the same communication channels common to two or more base stations B<b>1</b>, B<b>2</b>.

0057The system illustrated in <figref idref="DRAWINGS">FIG. 1</figref> has, for example, <b>128</b> communication channels as a whole to distributively assign them to the respective base stations. In the system which has two base stations as in <figref idref="DRAWINGS">FIG. 1</figref>, 64 channels may be equally assigned to each of the base stations B<b>1</b>, B<b>2</b>, or different numbers of communication channels may be assigned to the respective base stations, as required. The memory table <b>22</b> in <figref idref="DRAWINGS">FIG. 2B</figref> shows that 64 channels are equally assigned to each of the base stations B<b>1</b>, B<b>2</b>.

0058Reference is made to <figref idref="DRAWINGS">FIG. 3</figref> which shows a processing sequence performed in the radio communication system in accordance with the multi-channel access scheme of this embodiment.

0059This example will be described in connection with the system, as illustrated in <figref idref="DRAWINGS">FIG. 1</figref>, which has the base stations B<b>1</b>, B<b>2</b> accommodated in the line controller A<b>1</b>; the mobile stations C<b>1</b>, C<b>2</b> accommodated in the base station B<b>1</b>; and the mobile station C<b>3</b> accommodated in the base station B<b>2</b>.

0060First, the control unit <b>5</b> of the base station B<b>1</b> requests the line controller A<b>1</b> for assignment of an available communication channel through a channel request signal T<b>1</b> immediately after the base station B<b>1</b> has been activated. In response to the request, the line controller A<b>1</b> designates one of idle communication channels, if any, for the base station B<b>1</b>, and notifies the base station B<b>1</b> of the assignment through a channel notification signal T<b>2</b>. The control unit <b>5</b> of the base station B<b>1</b> holds information (communication channel assignment information) for identifying the communication channel notified (designated) from the line controller A<b>1</b> in a memory (the memory table <b>20</b> as shown in <figref idref="DRAWINGS">FIG. 2A</figref> in this example) within the base station B<b>1</b>. The other base station B<b>2</b> also performs a similar processing sequence.

0061Assume that after the communication channel assignment information on the communication channel to be next designated has been previously set in the base station B<b>1</b>, the mobile station C<b>1</b> accommodated in the base station B<b>1</b> makes a connection request for connection with the mobile station C<b>2</b> to the base station B<b>1</b> through a connection request signal T<b>11</b>.

0062In this event, in response to receipt of the connection request signal from the mobile station C<b>1</b>, the control unit <b>5</b> of the base station B<b>1</b> designates a communication channel identified by the communication channel assignment information held in the memory for a communication between the mobile station C<b>1</b> which is a calling party and the mobile station C<b>2</b> which is a called party, and notifies these mobile stations C<b>1</b>, C<b>2</b> of the designated communication channel through channel designation signals T<b>12</b><i>a</i>, T<b>12</b><i>b</i>, respectively.

0063Simultaneously with the foregoing designation (or with a certain time difference), the base station B<b>1</b> notifies the line controller A<b>1</b> of the connection through a connection notification signal T<b>13</b> in order to notify the line controller A<b>1</b> that the communication channel identified by the communication channel assignment information held therein has been assigned to the mobile stations C<b>1</b>, C<b>2</b> and in order to assign a communication channel to the mobile station C<b>3</b> located in the other base station B<b>2</b> (i.e., accommodated in the other base station B<b>2</b>). In other words, the connection notification signal T<b>13</b> provides the line controller A<b>1</b> with information on unconnected and connected mobile stations.

0064In response, the line controller A<b>1</b> recognizes that the base station B<b>1</b> has assigned the communication channel notified from the line controller A to the mobile stations C<b>1</b>, C<b>2</b>. In addition, when mobile stations accommodated in the other base station B<b>2</b> also include the mobile station C<b>3</b> which should be a called party, the line controller A<b>1</b> notifies, for example, the same communication channel (or a different but available communication channel) to the base station B<b>2</b> which accommodates the mobile station C<b>3</b>, which is a called party, through a channel notification signal T<b>14</b>. In this event, the base station B<b>2</b> designates a communication channel through a channel designation signal T<b>15</b> for the mobile station C<b>3</b>.

0065When the communication channel assignment information indicates that there is no communication channels which are held in the memory as undesignated for mobile stations (communication channels which have not yet been designated for mobile stations), i.e., when the base station B<b>1</b> has designated communication channels previously notified from the line controller A<b>1</b> to mobile stations, the base station B<b>1</b> immediately requests the line controller A<b>1</b> for assignment of a communication channel(s) through a channel request signal T<b>21</b>, and thereby receives the assignment of a communication channel(s) from the line controller A<b>1</b> through a channel notification signal T<b>22</b>, and holds the communication channel assignment information for preparation of the next communication.

0066From then on as well, the line controller A<b>1</b> repeats similar operations to control communication channels.

0067The channel designation signals T<b>12</b><i>a</i>, T<b>12</b><i>b</i>, T<b>15</b> from the base stations B<b>1</b>, B<b>2</b> to the mobile stations C<b>1</b>-C<b>3</b> are transmitted, for example, using a designated communication channel, but may be transmitted using another communication channel.

0068As described above, the radio communication system in accordance with the multi-channel access scheme of this embodiment has the line controller A<b>1</b>, one or plurality of base stations B<b>1</b>, B<b>2</b>, and a plurality of mobile stations C<b>1</b>-C<b>3</b> which share a plurality of communication channels, and assigns the communication channels to the mobile stations C<b>1</b>-C<b>3</b> as required. In this configuration, the radio communication system performs the communication channel control process as described below.

0069Specifically, the assignment of communication channels in response to connection requests from the mobile stations C<b>1</b>-C<b>3</b> is previously set from the line controller A<b>1</b> to the base stations B<b>1</b>, B<b>2</b>, and a connection response is sent back with a communication channel assigned from the base stations B<b>1</b>, B<b>2</b> in response to a connection request from the mobile stations C<b>1</b>-C<b>3</b>. In this way, it is possible to reduce a time required for the assignment of a communication channel to the mobile station C<b>1</b>-C<b>3</b> from the line controller A<b>1</b>, and to reduce a connection time for the mobile stations C<b>1</b>-C<b>3</b>. Also, the base stations B<b>1</b>, B<b>2</b> can designate the assignment of a communication channel in response to a connection request from the mobile station C<b>1</b>-C<b>3</b> in a short time.

0070Also, the radio communication system of this embodiment makes radio communications in accordance with the multi-channel access scheme in the following manner.

0071Specifically, one or two or more communication channels have been previously assigned to each of the plurality of base stations B<b>1</b>, B<b>2</b> as reserved channels in order to respond to a connection request from an arbitrary one of the mobile stations C<b>1</b>-C<b>3</b>. When an arbitrary one of the mobile stations C<b>1</b>-C<b>3</b>, which is a calling party, makes a connection request for a connection to one of the mobile stations C<b>1</b>-C<b>3</b> which is a called party location-registered (accommodated) in the same base station, the base station B<b>1</b> or B<b>2</b> responds to the connection request from the calling mobile station by designating the previously assigned reserved channel therefor, and also designates a reserved communication channel (or another one if there is no idle channel available) for the called mobile station. If the base station in which the calling mobile station is location-registered in a base station which is different from a base station in which the called mobile station is location-registered, the connection request from the calling mobile station is sent from the base station B<b>1</b> or B<b>2</b>, in which the calling mobile station is location-registered, to the line controller A<b>1</b> as a connection notification (T<b>13</b>). Upon receipt of the connection request, the line controller A<b>1</b> references the memory table <b>22</b>, and sends a connection request (channel notification T<b>14</b>) which designates a communication channel to be used to the base station B<b>1</b> or B<b>2</b> in which the called mobile station is location-registered. The designated communication channel in this event is a reserved communication channel or another communication channel if there is no reserved channel which is idle. Upon receipt of the connection request, the base station B<b>1</b> or B<b>2</b> transmits a connection response (channel designation T<b>15</b>) to the mobile stations C<b>1</b>-C<b>3</b> to which the connection request is directed. A call is placed through the communication channel designated by the foregoing processing procedure (control), thereby permitting the calling mobile station which has made the connection request to make a call to the called mobile station.

0072As appreciated from the foregoing, the radio communication system of this embodiment can provide at least advantages (1)-(4) as described below.

0073(1) When a connection request is made by an arbitrary one of the mobile stations C<b>1</b>-C<b>3</b> within the coverage area of a certain base station, the base station immediately responds to the connection request by designating a channel for the other mobile stations C<b>1</b>, C<b>2</b> or C<b>3</b>. Therefore, for example, when there is a single base station, it is possible to reduce a connection time from the connection request to the designation of a channel, for example, to approximately one-half as long as the conventional system, for example, for a communication between the mobile stations C<b>1</b>-C<b>3</b> which lie within the coverage area of the single base station.

0074(2) When there is a single base station, a comfortable operability can be provided for the operators (users) of the mobile stations C<b>1</b>-C<b>3</b> because of a reduction in a connection waiting time.

0075(3) Even when there are a plurality of base stations B<b>1</b>, B<b>2</b>, the advantages (1), (2) can be provided for a communication between mobile stations which lie within the coverage area of the same base station B<b>1</b> or B<b>2</b>.

0076(4) When a communication is made between the mobile stations C<b>1</b>-C<b>3</b> which lie in the coverage areas of different base stations B<b>1</b>, B<b>2</b>, a connection waiting time is reduced particularly for a calling user.

0077As described above, in the radio communication system of the first embodiment, in which the line controller A<b>1</b> manages or keeps track of communication channels for assignment to communications, the line controller A<b>1</b> has previously notified each of the base stations B<b>1</b>, B<b>2</b> of a communication channel which should be assigned for the next connection request, so that when the next connection request is made from any of the mobile stations C<b>1</b>-C<b>3</b>, the base station B<b>1</b> or B<b>2</b> can directly designate the communication channel, thereby making it possible to reduce a time taken to designate a communication channel for the mobile stations C<b>1</b>-C<b>3</b>, and to reduce a communication connection time required up to the assignment of a communication channel. It is therefore possible to quickly designate a communication channel for a mobile station in response to a connection request from a mobile station.

0078In the foregoing embodiment, the channel controller A<b>1</b> has previously assigned idle channels (unused communication channels) to the base stations B<b>1</b>, B<b>2</b> to complete a connection of a calling mobile station C<b>1</b>, C<b>2</b> or C<b>3</b> with the base station which is location-registered with the calling mobile station in a short time, so that the connection can be promptly completed (for example, within 0.3 seconds) to accomplish a high speed access. Similarly, a connection can be completed in a short time for a called mobile station C<b>1</b>-C<b>3</b> which belongs to the same base station B<b>1</b> or B<b>2</b>. Further, even when the called mobile station is accommodated in the base station B<b>1</b> or B<b>2</b> which is different from the base station B<b>2</b> or B<b>1</b> which accommodates the calling mobile station, a final connection can be quickly completed (for example, within 0.8 seconds). In this event, the base station B<b>1</b> or B<b>2</b> which accommodates the calling mobile station immediately responds to a connection request from the mobile station C<b>1</b>, C<b>2</b> or C<b>3</b> and then performs operations for establishing an actual call spreading across the base stations B<b>1</b> and B<b>2</b>. Stated another way, the calling mobile station C<b>1</b>-C<b>3</b> receives a response signal as if a connection has been immediately made, followed by the actual connection which is made across the base stations B<b>1</b> and B<b>2</b>. In this way, even in regard to a call over different base stations, a calling user at least apparently feels that the call can be immediately made, and can therefore enjoys a call without any stress.

0079Here, in the foregoing embodiment, the line controller A<b>1</b> previously notifies the base stations B<b>1</b>, B<b>2</b> of the assignment of communication channels so that the base stations B<b>1</b>, B<b>2</b> set the communication channels as candidates. Additionally, the assigned communication channels set in the base stations B<b>1</b>, B<b>2</b> (communication channel assignment information in this embodiment) may be deleted or modified at any time by a control signal or the like from the line controller A<b>1</b> in accordance with a particular communication situation or the like, by way of example.

0080Also, when a plurality of available communication channels have all been assigned so that there is no communication channel available, the line controller A<b>1</b> cannot assign any communication channel, but the line controller A<b>1</b> may forcedly create an idle communication channel for assignment depending, for example, on a communication situation or the like.

0081Also, as in the foregoing embodiment, a communication may be made by performing at all times the radio channel control scheme which involves a previously notification of the assignment of communication channels from the line controller A<b>1</b> to the base stations B<b>1</b>, B<b>2</b> for setting them as candidates. Alternatively, the communication channel control scheme of this embodiment may be switched to or conducted in combination with another communication channel control scheme (for example, a normal scheme in which the line controller A<b>1</b> assigns a communication channel after a connection request is made from any of the mobile stations C<b>1</b>-C<b>3</b>) in response to an instruction signal generated by any of the line controller A<b>1</b>, base stations B<b>1</b>, B<b>2</b>, mobile stations C<b>1</b>-C<b>3</b>, and other communication devices included in the radio communication system. This is because a quick connection is not necessarily required for all calls in general.

0082It should be understood that the radio communication system as described in the foregoing embodiment is not limited to a communication system in an airport, but can be applied to general digital communications.

0083In the mobile stations C<b>1</b>-C<b>3</b>, a connection requesting unit is implemented by a function of transmitting the connection request signal T<b>11</b> over the air.

0084Also, in the line controller A<b>1</b> of the foregoing embodiment, a designated communication channel notification unit is implemented by a function of previously notifying the base stations B<b>1</b>, B<b>2</b> of communication channels to be designated by generating the channel notification signals T<b>2</b>, T<b>22</b>.

0085Also, in the base stations B<b>1</b>, B<b>2</b> of the foregoing embodiment, a designated communication channel identification information storage unit is implemented by a function of storing information for identifying a communication channel to be designated in the future in the memory table <b>20</b> as shown in <figref idref="DRAWINGS">FIG. 2A</figref> (the communication channel assignment information in this embodiment); a connection request receiver unit is implemented by a function of receiving the connection request signal T<b>11</b> generated from the mobile stations C<b>1</b>-C<b>3</b> over the air; and a communication channel designation unit is implemented by a function of generating the communication channel designating signals T<b>12</b><i>a</i>, T<b>12</b><i>b </i>for designating a communication channel for the mobile stations C<b>1</b>-C<b>3</b>.

0086In the base stations B<b>1</b>, B<b>2</b> of the foregoing embodiment, on the other hand, a connection notification unit is implemented by a function of generating the connection notification signal T<b>13</b> for notifying the line controller A<b>1</b> of a connection situation with the mobile stations C<b>1</b>-C<b>3</b>; and a connection communication channel designation unit is implemented by a function of generating the channel designation signal T<b>15</b> for designating a communication channel for the mobile station C<b>1</b>-C<b>3</b> which takes the position of a connection requested party through a connection request.

0087Further, in the line controller A<b>1</b> of the foregoing embodiment, a connection communication channel notification unit is implemented by a function of generating the channel notification signal T<b>14</b> for notifying a communication channel to be designated for a base station (another base station) different from a base station which receives a connection request.

0088Also, in the base stations B<b>1</b>, B<b>2</b> of the foregoing embodiment, a designated communication channel notification request unit is implemented by a function of generating the channel request signals T<b>1</b>, T<b>21</b> for requesting the line controller A<b>1</b> to notify a communication channel to be designated.

0089A second embodiment of the present invention will now be described with reference to <figref idref="DRAWINGS">FIGS. 1 and 4</figref>.

0090In this embodiment, in the radio communication system illustrated in <figref idref="DRAWINGS">FIG. 1</figref>, a connection request made from any of the mobile stations C<b>1</b>-C<b>3</b> is preferentially handled by preferentially using one of communication channels previously assigned to the base stations, as described in the first embodiment.

0091<figref idref="DRAWINGS">FIG. 4</figref> shows an example of a connection request signal generated by the mobile stations C<b>1</b>-C<b>3</b>.

0092The connection request signal in the second embodiment includes connection request information indicative of a connection request; and preference information indicative of whether or not the associated connection request should be preferentially handled. The mobile stations C<b>1</b>-C<b>3</b> each can control the preference information included in the connection request signal transmitted to the base station B<b>1</b> or B<b>2</b> over the air to switch between a connection request signal which should be preferentially handled and a connection request signal (for example, normal) which should not be preferentially handled for transmission over the air. The setting as to whether a particular connection request is preferential or not may be made by an arbitrary means such as by depressing a setting button provided on the mobile station.

0093A variety of formats may be used for the connection request signal.

0094In this embodiment, the preference information included in the connection requests signal generated from the mobile stations C<b>1</b>-C<b>3</b> is analyzed by the base stations B<b>1</b>, B<b>2</b> or line controller A<b>1</b>. When the connection request signal includes the preference information which indicates that the request should be preferentially handled, a communication channel previously assigned to the base station B<b>1</b> or B<b>2</b> is preferentially assigned to a mobile station C<b>1</b>-C<b>3</b> which has generated the connection request signal and a mobile station C<b>1</b>-C<b>3</b> which is in a position of a connection requested party. When the connection request signal generated from the mobile station C<b>1</b>-C<b>3</b> does not include the preference information which indicates that the request should be preferentially handled, a communication channel may be assigned, for example, such that the line controller A<b>1</b> references the memory table <b>22</b> to assign an idle communication channel after the connection request has been made from the mobile station C<b>1</b>-C<b>3</b>.

0095As described above, in the radio communication system in accordance with the multi-channel access scheme of this embodiment, when a connection request from an arbitrary mobile station C<b>1</b>-C<b>3</b> to another arbitrary mobile station C<b>1</b>-C<b>3</b> includes a signal indicative of a preferential connection, a predetermined communication channel is preferentially assigned to a connection of the other arbitrary mobile station C<b>1</b>-C<b>3</b> with a base stations B<b>1</b>, B<b>2</b> which is registered with that mobile station C<b>1</b>-C<b>3</b>. Alternatively, for example, an ongoing call may be forcedly interrupted, such that the connection is made using a communication channel which has been used for that call. This strategy will be described in detail in the next embodiment.

0096Accordingly, a mobile station C<b>1</b>-C<b>3</b> which requires, for example, an urgent communication or call can preferentially secure a communication channel between the mobile station and a connection requested party to immediately start a communication by generating a connection request signal which includes information indicating that a preferential connection is required.

0097The base stations B<b>1</b>, B<b>2</b> or line controller A<b>1</b> in this embodiment comprises a preferential connection control unit which is implemented by a function of preferentially designating a communication channel based on information indicative of the priority (the preference information in this embodiment) included in a connection request made from the mobile station C<b>1</b>-C<b>3</b> when the connection request should be preferentially handled.

0098A third embodiment of the present invention will be described with reference to a flow chart of <figref idref="DRAWINGS">FIG. 5</figref>.

0099In this embodiment, in the radio communication system illustrated in <figref idref="DRAWINGS">FIG. 1</figref>, where a connection request made from any of the mobile stations C<b>1</b>-C<b>3</b> can be preferentially handled in response to the connection request signal including the preference information as shown in <figref idref="DRAWINGS">FIG. 4</figref>, an idle communication channel is secured when all communication channels are being occupied.

0100Reference is made to <figref idref="DRAWINGS">FIG. 5</figref> which illustrates an exemplary processing procedure performed in the radio communication system of the third embodiment.

0101First, as any of the mobile stations C<b>1</b>-C<b>3</b> generates a connection request signal (step S<b>1</b>), the connection request signal is received by the base station B<b>1</b> or B<b>2</b> which is location-registered with (accommodates) the mobile station C<b>1</b>, C<b>2</b> or C<b>3</b>. Then, the base station B<b>1</b> or B<b>2</b> or the line controller A<b>1</b> determines based on the preference information included in the connection request signal whether or not the connection request signal requests a preferential connection (step S<b>2</b>). As a result, if the connection request signal does not request a preferential connection, a normal connection is made (step S<b>6</b>).

0102On the other hand, when the connection request signal requests a preferential connection, the base station B<b>1</b> or B<b>2</b> or the line controller A<b>1</b> determines whether or not communication channels are fully occupied between the calling mobile station C<b>1</b>, C<b>2</b> or C<b>3</b> and the base station B<b>1</b> or B<b>2</b> which has location-registered the mobile station C<b>1</b>, C<b>2</b> or C<b>3</b>, and whether or not communication channels are fully occupied between a called mobile station C<b>1</b>, C<b>2</b> or C<b>3</b> and the base station B<b>1</b> or B<b>2</b> which has location-registered the called mobile station C<b>1</b>, C<b>2</b> or C<b>3</b> (step S<b>3</b>). These determinations can be made, for example, by referencing the memory table <b>22</b> of the line controller A<b>1</b>. As a result of the determinations, when the communication channels are not fully occupied between the mobile station C<b>1</b>, C<b>2</b> or C<b>3</b> and the base station B<b>1</b> or B<b>2</b>, i.e., when there is an idle communication channel, the connection is preferentially made using the idle communication channel (step S<b>7</b>).

0103On the other hand, when the communication channels are fully occupied between the mobile station C<b>1</b>, C<b>2</b> or C<b>3</b> and the base station B<b>1</b> or B<b>2</b>, a communication made by another mobile station or the like through any communication channel is disconnected (step S<b>4</b>), for example, in accordance with a predefined condition, and the requested connection is preferentially made using the freed communication channel resulting from the disconnection (step S<b>5</b>). In this event, the base station B<b>1</b> or B<b>2</b> notifies the other mobile station of a preferential connection, and subsequently disconnects the communication channel after the lapse of a predetermined time period.

0104Now, examples will be given to the predefined condition under which “any communication channel is disconnected” at step S<b>4</b> when “the communication channels are fully occupied,” as determined at step S<b>3</b>.

EXAMPLE 1

0105among communication channels with the preference flag set at “0” (indicative of a normal connection), a communication channel is selected in order from the one having the smallest channel number (or the largest channel number) and is disconnected.

EXAMPLE 2

0106among communication channels with the preference flag set at “0” (indicative of a normal connection), a communication channel which has been used for a long time is selected and disconnected. In this event, the base station should store the order in which the idle/occupied flag is set to “1” in each connection request, or measure a time period for which the busy/idle flag remains at “1.”

0107Further, when any communication channel is to be disconnected, a signal indicative of the disconnection may be multiplexed on speech data communicated on the communication channel, so that the operator of the mobile station in communication can previously know that the communication will be disconnected by generating, for example, a speech saying “the communication will be disconnected” during a call which is being made using the mobile station through the communication channel.

0108Whether the communication channels are fully occupied or not may be determined, for example, based on the communication channel management performed by the base stations B<b>1</b>, B<b>2</b> and line controller A<b>1</b> (with reference to the memory table <b>22</b> in <figref idref="DRAWINGS">FIG. 2B</figref> or the like). Alternatively, if no information for identifying a communication channel to be next designated (communication channel assignment information) is not stored in the memory table as shown in <figref idref="DRAWINGS">FIG. 2A</figref>, provided in the base stations B<b>1</b>, B<b>2</b>, a determination can be made that there is no idle communication channel, i.e., the communication channels are fully occupied.

0109As described above, in the radio communication system in accordance with the multi-channel access scheme of this embodiment, when the communication channels are fully occupied at the time a connection request signal indicative of a preferential connection is generated from a certain mobile station C<b>1</b>, C<b>2</b> or C<b>3</b>, the associated base station sends a signal which indicates that a preferential connection is requested to another mobile station which is in connection through a predetermined communication channel, and disconnects the communication (for example, in a certain time period) to establish a communication channel for the mobile station C<b>1</b>-C<b>3</b> which has requested for the preferential connection.

0110Therefore, even if there is no idle communication channel, i.e., all the communication channels are fully occupied at the time a connection request signal is generated from a mobile station C<b>1</b>-C<b>3</b>, which needs to make an urgent communication or call, in order to preferentially establish a connection therefor, the base station or line controller aborts a communication through a communication channel used by another mobile station or the like and preferentially uses the communication channel freed thereby for a connection associated with the urgent communication, so that the communication channel can be preferentially secured between the mobile station which has requested the urgent connection and a connection requested party, thus permitting the mobile station to start a communication.

0111Each of the base stations B<b>1</b>, B<b>2</b> and line controller A<b>1</b> comprises a preferential connection control unit which is implemented by a function of preferentially handling a connection request generated from the mobile station C<b>1</b>, C<b>2</b> or C<b>3</b> based on information indicative of the priority (the preference information in this embodiment) included in the connection request by interrupting a communication to ensure an idle communication channel when there is no idle communication channel, and then preferentially designating the communication channel.

0112The radio communication system, line controller, base station, mobile station and the like according to the present invention are not necessarily limited to the configurations shown above, but may be implemented in a variety of configurations. Also, the present invention can provide the method or scheme for executing the processes according to the present invention, a program for implementing such a method and scheme, a recording medium which has recorded the program thereon, and the like. The present invention can further provide a variety of apparatuses and systems which implement the foregoing method and scheme.

0113The present invention is not necessarily limited to the field of applications shown above, but can be applied to a variety of applications.

0114A variety of processes executed by the radio communication system, line controller, base station, mobile station and the like may be controlled, for example, by a processor which executes a control program stored in a ROM (Read Only Memory) included in hardware resources which comprise the processor, memory and the like. Alternatively, respective function units which execute associated processes may be implemented by independent hardware circuits.

0115The present invention can also take the form of a computer readable recording medium such as a floppy (registered trademark) disk, CD (Compact Disc)-ROM or the like which stores the control program, or the program itself, in which case the processes associated with the present invention can be carried out by loading the control program from the recording medium into a computer and having a processor execute the control program.

0116It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.